Matthew Walker [ UC Berkeley ] It’s a delight and privilege to be here and I would like to start with testicles. Men who sleep 5 hours a night have significantly smaller testicles than those who sleep 8 hours or more. In addition men who routinely sleep 5 to 6 hours a night will have a level of testosterone which is that of someone 10 years their senior.
This is the best news that I have for you today.
From this point forward it’s only going to get worse.
Rather than tell you about the wonderfully good things that happen when you get sleep, I’m going to tell you about the alarmingly bad things that happen when you don’t get enough, both for the brain and for the body.
Let me start with the brain and the functions of learning and memory.
Sleep and Learning & Memory
What we’ve discovered over the past 10 or so years is that you need sleep after learning to essentially hit the Save button on those new memories so that you don’t forget.
Sleep essentially future proofs those facts within the brain.
But recently we’ve discovered that you not only need to sleep after learning you also need sleep before learning – but now to actually prepare your brain, almost like a dry sponge ready to initially soak up new information.
And without sleep the memory circuits of the brain effectively become waterlogged, as it were, and you can’t absorb new information.
Here in this study, we decided to test the hypothesis that pulling the all nighter was a good idea. How do you do that well? We took a group of healthy adults and we assigned them to one of two experimental conditions: a sleep group and a sleep deprivation group.
The sleep group are going to get a full eight hours of shut-eye but the deprivation group, we’re going to keep them awake in the laboratory under full supervision. There’s no naps there’s no caffeine. It’s miserable for everyone included us as well.
Then, the next day, we’re going to place those participants inside an MRI scanner and we’re going to have them try and learn a whole list of new facts – as we’re taking snapshots of brain activity.
Then we’re going to test them to see how effective that learning has been and that’s what you’re looking at here, on the vertical axis, the amount of learning.
So the higher up you are, the more you learn.
When you put those two groups head-to-head, what you find is a quite significant 40% deficit in the ability of the brain to make new memories without sleep.
I think this should be frightening considering what we know is happening to sleep in our education populations right now
Just a frame this in context, it would be the difference between acing an exam and failing it miserably.
And we’ve gone on to discover what goes wrong within your brain to produce these types of learning disabilities.
There is a structure on the left and the right side of your brain called the hippocampus – and you can see it here in these sort of orange yellow colors. Think of the hippocampus like the informational inbox of your brain. It’s very good at receiving new memory files and holding on to them. When we looked at this structure, in those people who’d had a full night of sleep – here in green, we saw lots of healthy learning related activity.
Yet in those people who were sleep deprived we actually couldn’t find any significant signal whatsoever.
It’s almost as though sleep deprivation had shut down.
The memory inbox and any new incoming files were just being bounced.
You couldn’t effectively commit new experiences to memory.
Parenthetically – I should note – if you would like to know what life is like without a functioning hippocampus, just watch the movie memento.
I suspect many of you have seen this.
This gentleman suffers brain damage and from that point forward he can no longer make any new memories. He’s what we call densely amnesic.
The part of his brain that was damaged was the hippocampus and it is the very same structure that sleep deprivation will attack and block your brains capacity for new learning.
So that’s the bad that happens when you take sleep away.
Let me just come back to that control group for a second. Do you remember those folks that got a full 8 hours of sleep?
We can ask a very different question here. What is it about the physiological quality of sleep, when you do get it, that actually enhances and restores your learning and memory ability, each and every day?
By recording sleep, with electrodes placed all over the head, we’ve discovered that there are big powerful brain waves that happen during the very deepest stages of sleep that have riding on top of them, these spectacular bursts of electrical activity called Sleep Spindles.
It’s the combined quality of these Deep Sleep Brain Waves at night – that acts like a file transfer mechanism –it takes memories from a short-term vulnerable reservoir and shifts them to a more permanent long-term storage site within the brain called the cortex – this big wrinkled massive tissue that sits on the top of your brain.
It means that when you wake up the next morning there are two benefits.
First, having shifted memories of yesterday to that long-term Safe Storage Haven in the brain, they are protected – so that you will remember rather than forget.
The second benefit, however, is that having shifted those files from that short-term reservoir – almost like moving files from a USB stick – you’ve cleared out all of that memory encoding capacity, so that when you wake up the next day you can start acquiring new files all over again.
You can start learning anew.
So its this elegant beautiful symbiotic system of memory that happens each and every night.
It’s important that we understand what, during sleep, actually transacts these memory benefits – because there are real medical and societal implications.
Aging & Dementia
Let me just tell you about two areas that we’ve moved this work out into.
I’ll begin clinically, and specifically, with the context of Aging and Dementia. Because I think many of us have a sense or even know that as we get older our learning and memory abilities start to fade. They begin to decline.
But what we’ve also known for many decades is that a physiological signature of Aging is that your sleep gets worse and not just any type of sleep especially that deep quality of sleep that I was just describing.
Only last year, we finally published evidence that these two factors are not simply co-occurring, they are significantly interrelated.
It suggests that the disruption of deep sleep is perhaps an underappreciated factor that is contributing to what we call cognitive decline or memory decline in Aging and most recently, we’ve discovered, in Alzheimer’s disease as well.
I know this is remarkably depressing news.
I understand it’s in the mail – it’s coming at you.
But there is a potential silver lining here.
Unlike many of the other factors that we know are associated with Aging and Dementia – for example changes in the physical structure of the brain, or even changes in the vasculature of the brain. Those are fiendishly difficult to treat right now. We don’t have any good wholesale approaches in medicine.
That sleep is a missing piece in the explanatory puzzle of Aging and Alzheimer’s is exciting because we may be able to do something about it.
One way that we are approaching this, at my sleep center, is – not by using sleeping pills by the way (they are blunt instruments that do not produce naturalistic sleep and they have been associated with a higher risk of death and cancer – and I’m happy to speak about that evidence during the Q&A; and it’s discussed in the book as well).
What we are actually doing is developing a method based on this technology. It’s called Direct Current Brain Stimulation. It sounds like the stuff of science fiction.
It’s actually science fact.
You apply electro pads to the head and you insert a small amount of voltage into the brain – so small that you tend not to feel it. But it has a measurable impact on physiology.
If you apply this stimulation during sleep, in young healthy adults – as if you’re sort of singing in time with those deep sleep brainwaves – not only can you actually amplify the size of those deep sleep brainwaves but in doing so you can almost double the amount of memory benefit that you get from sleep.
The question now is whether we can translate the same affordable, potentially portable technology into older adults and those with dementia.
Can we restore back some healthy quality of deep sleep and in doing so can we salvage aspects of learning and memory function?
That is my real hope now. That’s one of our moonshot goals, as it were.
I should note, by the way – because I always get asked this question people will say where can I buy one of those devices, I want one yesterday and I want 5 more tomorrow – they are not yet FDA approved for use in sleep.
You can buy them on the Internet. I strongly advise against that.
Just read around. Some horror stories: people have misaligned the voltage, skin burns, they’ve lost their eyesight for several days.
Hang on, we are desperately trying to bring this to fruition as soon as we can.
So that’s sleep and memory in a clinical context
The Edina Study
But let me speak about sleep and memory in society and specifically – here – within education. Because if sleep really is so important for learning and memory, then enhancing sleep, in a context where arguably it matters most, should prove transformative.
And it has.
There are several counties throughout the United States that have started to delay the school start times and then measure the academic consequence
one of the earliest test case examples happened in Edina, Minnesota. It’s a Township that sits just outside of Minneapolis. They shifted their school start times from 7:25 in the morning to 8:30 in the morning.
By the way, what are we doing trying to educate our next generation at 7:25 in the morning?
To give you a sense of this: buses for a 7:25 start time will often begin leaving at 5:30 in the morning. That means that some kids are having to wake up at 5:15, 5 o’clock – maybe even earlier.
This is lunacy.
But in Edina, it was the beginnings of a movement.
The metric that they used, to assess the academic consequence, was the SAT scores.
They focused their analysis on the top 10% performing students – arguably those that have the least to gain in terms of any further improvement by way of sleep.
In the year before they made the time change, that top 10% performing students got an average score of 1288 – which is a very respectable score.
The following year, when students were now going to school at 8:30 in the morning, the average SAT score was 1500.
That is a 212 point increase – which is non-trivial. That will change which tier of university those school kids end up going to and perhaps, as a consequence, their subsequent life trajectories.
Some people have questioned aspects of the Edina Study, and I think for perhaps good reason, but in all of the subsequent carefully controlled studies the data is unequivocal, I think.
- Academic grades increase
- behavioral problems decrease
- truancy rates decrease and
- psychological and psychiatric issues also decrease.
But something else actually happened in this story of later school start times and it was something that we did not anticipate.
The life expectancy of students actually increased.
You think, “I don’t understand, how does that work?”
Does anybody know what the leading cause of death in late stage teenagers is?
Throughout most developed nations?
Suicide is actually second. It’s car crashes – and here sleep matters enormously.
Another example comes from TetonCounty in Wyoming
They shifted their school starts from 7:35 in the morning to 8:55 in the morning and then they measured the reduction in car crashes in this narrow age of just 16 to 18
The only thing perhaps more remarkable than the extra hour of sleep that those students reported getting was the drop in vehicle accidents.
There was a 70% reduction.
Just to sort of frame that in context, the advent of ABS technology – what we call anti-lock braking systems, that prevent your wheels from locking up and hard braking, so that you can still safely maneuver a vehicle – that dropped accident rates by 20 to 25%.
Some deemed it to be a revolution.
Here is a biological factor, sleep, that will drop accident rates by up to 70%.
I think it’s time for us to reconsider the importance of sleep in education.
When sleep is abundant Minds flourish.
If our goal as educators truly is to educate, and not risk lives in the process, then I fear that we may be failing our children in a significant manner with this incessant model of early school start times.
So that’s sleep for Learning, Memory, Aging and Alzheimer’s – what else is sleep good for?
Sleep is essential to help stabilize your emotional and mental health. Without sleep the emotional circuits of your brain become hyperactive and irrational.
Allow me to demonstrate with a sleep-deprived subject.
We do video diaries with our participants throughout the deprivation night. Meet one under the pseudonym of Jeff. It’s 11:30 at night. Jeff has been awake for about 16 hours.
I’m going to plug in the audio here to see if I can get you some audio playing out.
Jeff’s just entered the study. He’s been awake for a normal 16 hours. Let’s hear from Jeff what his hopes and aspirations are for the deprivation period
“It’s about 11:27 right now. I’ve been here for about and I think about an hour. No, yeah. About an hour. So it’s the first hour. I’m writing my paper right now – 30 page paper. Hopefully I can get some of it done before I get too sleepy”
So that’s Jeff. Perfectly likable, affable chap who’s hoping to get his 30 page report complete in a night of sleep deprivation.
Classic delusional undergraduate thinking, I have to say. I see it all of the time in my students
Now let’s fast-forward the clock. It’s now 5:30 the following morning. Jeff is now been awake for 22 hours straight. Instantly you’ll notice one of the hallmark features of sleep deprivation which is that you actually slide down in your chair – you can just you can look around the room right now actually – and see Jeff’s down about 6 or 7 inches. It’s about an inch for every hour that you’ve been awake beyond the standard 16 (based on our highly sophisticated machine learning algorithms).
But, in all seriousness, notice how emotionally different Jeff has become. Some people have, I think, perhaps unkindly, described him as becoming a little bit emotionally unhinged.
Let’s hear how that 30 page report has been going – and I do apologize ahead of time for the profanity.
“Hello. I’m very angry right now. Because I didn’t get any f*cking . . . oh can I curse on this? Are they going to like . . . whatever [laughs maniacally] [inaudible]. I’m very lucid actually.”
Did you notice how Jeff went from being remarkably upset and annoyed – that he got none of his 30 page report complete – then finding it almost hilarious?
He was nearly punch-drunk giddy on sleep deprivation and then came right back down to baseline again.
That is a remarkably abnormal emotional distance to travel within such a short time period.
I think it emphasizes the type of destabilizing influence that a lack of sleep has on our emotional integrity.
We’ve since discovered what actually changes within your brain to produce this type of pendulum emotional irrationality.
There’s a structure very deep within your brain called the amygdala – you can see it here in these red colors.
Again you have one on the left side and one on the right.
The amygdala is one of the centerpiece regions for the generation of strong emotional reactions – including negative reactions.
When we looked at this structure in those people who’d had a full night of sleep – here in green – we saw a nice controlled modest degree of reactivity.
Yet in those people who are sleep deprived we saw this amplified – almost aggravated degree of reactivity
The amygdala was actually 60% more responsive under conditions of a lack of sleep.
It’s almost as though without sleep we’ve become all emotional gas pedal with too little regulatory control brake.
But what is perhaps more concerning, however, is that this represents a neurological signature that is not dissimilar to numerous psychiatric conditions.
We’re now finding significant links between sleep disruption and conditions such as depression, anxiety –including PTSD, schizophrenia and, tragically, suicide as well.
In fact we cannot find a single psychiatric condition in which sleep is normal.
I think sleep has a profound story to tell in our understanding, in our treatment and perhaps even may contribute to our ultimate prevention of grave mental illness.
So that’s sleep for the brain but sleep is just as essential for your body.
Immune Cell Activity
Here I could have gone into any one of the model systems and spoken about it in detail – we’ve already spoken a little bit about sleep loss and the reproductive system – I could tell you about sleep loss and the metabolic system.
After one week of short sleep your blood sugar levels are disrupted so significantly that your doctor would classify you as being pre-diabetic.
I could tell you about sleep loss and the cardiovascular system: all it takes is one hour.
There is a global experiment that is performed on 1.6 billion people across 70 countries twice a year and it’s called daylight savings time
In the spring, when we lose one hour of sleep, we see a subsequent 24% increase in heart attacks
In the fall when we gain an hour of sleep we see a 21% decrease in heart attacks.
That is how fragile your body is to even just the smallest perturbations of sleep.
I think many of us perhaps don’t think anything of losing an hour of sleep. But as a deep dive I actually want to focus on this in the immune system.
Here I’ll introduce these delightful blue elements in the image they are called natural killer cells
Think of natural killer cells like The Secret Service agents of your immune system.
They are very good at identifying dangerous foreign elements and eliminating them.
In fact, what they’re doing here –in this image–is embedding themselves into a malignant a cancerous tumor mass and destroying it.
Many of you may not know this, but today your body produced cancer cells – and it’s always doing this.
What stops those cancer cells from becoming the disease that we call cancer is in part these natural killer cells.
So what you want is a virile set of these immune assassins at all times and, sadly, that’s exactly what you don’t have – if you’re not sleeping enough.
So here in this study, from my wonderful colleague Mike Erwin. You’re not going to have your sleep deprived for an entire night – you’re simply going to have your sleep restricted to four hours for one single night, and then we’re going to look to see what is the percent reduction in immune cell activity that you suffer.
It’s not small. it’s not 10%. It’s not 30%. There was a 70% drop in natural killer cell activity.
That’s quite a concerning state of an immune deficiency and it happens quickly – essentially after just one bad night.
Imagine the state of your immune system after weeks – if not months of insufficient sleep – and it perhaps should then come as no surprise to learn that we now have significant links between short sleep and numerous forms of cancer.
Currently that list includes
- cancer of the bowel
- cancer of the prostate and
- cancer of the breast.
In fact the link between a lack of sleep and cancer is now so strong that recently the World Health Organization decided to classify any form of nighttime shift work as a probable carcinogen.
In other words jobs that may induce cancer – because of a disruption of your sleep wake rhythms.
You may have heard of that old maxim, “you can sleep when you’re dead.”
I’m being absolutely serious. It is mortally unwise advice. Because if you adopt that mindset we know, from the data, that you will now live a shorter life and the quality of that shorter life will be significantly worse.
Epidemiological studies teaches this: short sleep predicts a shorter life. It predicts all-cause-mortality.
And the bad news, I’m sorry keeps coming, because if you are fighting a battle against cancer, and not getting sufficient sleep, that cancer may grow more quickly and aggressively.
So here I actually want to feature work not from my own sleep center but by a scientist called David Gozal, who works at the University of Chicago.
He examines the relationship between sleep loss and cancer in mice.
I know this isn’t for everyone, so I will tell you when to look away if you prefer not to see this.
In one of the studies that he did he inoculated some mice with cancer cells on their back and then he gave that cancer a one-month period to grow. At the end of that one month, he resected the skin and measured the size of that tumor mass.
Half of the mice were allowed to sleep normally, during that one-month period, the other half had their sleep disrupted. Not total deprivation, they just sort of played with them a little bit more during the day and during the night, to restrict their sleep.
In a second I’m going to play a video with David illustrating the results. Now would be the time to look away if you would prefer to do so
Here you can see him pointing to a mouse on a monitor with the skin resected – and you can clearly see that tumor mass there.
This is in one of the mice that was allowed to sleep normally during that one month.
I’ll play the video and he’ll reveal behind it another mouse.
That mouse was in the sleep restriction group and you will see the difference in the tumor mass.
This is the difference.
There was a 200% increase in the speed and the size of that cancerous growth linked to insufficient sleep
Worse still, the cancer in those underslept mice had actually metastasized.
That’s just a medical description meaning that it had breached the point of origin and started to invade other areas – bone, other organs as well as brain.
When cancer becomes metastatic – that’s when we see mortality rates escalate.
So if you are fighting a battle against cancer, and not getting sufficient sleep, it may be the equivalent of placing gasoline on an already aggressive fire
Sleep loss is an accelerant and we now know that it produces a harmful biological fertilizer for the more rapid and rampant growth of cancer.
If increasing your risk of developing Alzheimer’s or cancer by way of a lack of sleep were not sufficiently disquieting we have since discovered that a lack of sleep will even erode the very fabric of biological life itself.
Your DNA genetic code.
So here in this study, they took a group of healthy adults and limited them to 6 hours of sleep for one week
And then they measured the change in the gene activity profile, compared to when those same individuals were getting eight hours of sleep for a week.
There were two critical results here
First, a sizable and significant 711 genes were distorted in terms of their activity caused by 6 hours of sleep
And that’s relevant by the way.
We know that almost 1 out of every 2 American adults are trying to survive on 6 hours of sleep or less during the week.
The second result was that about half of those genes were actually increased in their activity.
The other half were actually decreased in their activity.
Those genes that were decreased by a lack of sleep were genes related to numerous aspects of the immune system – which fits very well with the evidence I was just discussing regarding cancer.
Those genes that were actually increased in their activity – or what we call up-regulated in their expression – were genes related to the promotion of tumors, genes that were related to chronic inflammation within the body and also genes that were related to stress and as a consequence cardiovascular disease.
I think many individuals in society feel uncomfortable about the idea of genetically modified embryos or even genetically modified food but by choosing to get insufficient sleep we may be forced to accept that we are performing a similar genetic modifying experiment on ourselves.
If we don’t let our children get the sleep that they so desperately need then we may be inflicting a similar genetic engineering experiment on them as well.
There is simply no aspect of your physiology that seems to be able to retreat at the sign of sleep deprivation and get away unscathed.
It’s almost like a broken water pipe in your home.
Sleep loss will leak down into every nook and cranny of your biology – even tampering with the very DNA nucleic alphabet that spells out your daily health narrative.
So where does this leave us?
What is the piece of mental furniture I would like to gift to you as we finish the talk?
Well it would be this: sleep is not an optional lifestyle luxury.
Sleep is a non-negotiable biological necessity
It’s a life support system and it is mother nature’s best effort yet at contra death.
The decimation of sleep throughout industrialized nations is having a catastrophic impact on our health our wellness and the safety and the education of our children.
It’s a silent sleep loss epidemic and it is fast becoming one of the greatest public health challenges that we now face in the 21st century.
I believe it is now time for us to reclaim our right to a full night of sleep – without embarrassment and without that terrible stigma of laziness.
In doing so we may finally remember what it feels like to be awake during the day.
With that soap box rant over, I will simply say good night, good luck and – above all – I do hope you sleep well.
FEATURED IMAGE CREDIT: Tambako the Jaguar